A respiration system of the type appears from EP 643 978 B1. It comprises a housing provided with gas ducts and a cover plate, which seals the interior space of the housing against the environment. To form the gas ducts, the housing has partitions, which extend, starting from the bottom of the housing, vertically up to the top side of the housing. To seal the gas ducts, the cover plate is provided with packing gaskets (cords) or seals, which extend corresponding to the partitions. The cover plate is screwed to the housing. The packing cords lie on the front sides of the partitions. Great rigidity of both the housing and the cover plate is required for this design of the respiration system in order to obtain uniform pressing of the sealing area, because differences in height can be compensated via the packing cords to a limited extent only. The manufacture of the prior-art cover is complicated because the packing cords must be vulcanized with precision into grooves prepared in advance in the cover plate.